Question

Which one of the following is the correct order of increasing size?

• A. $Mg<Na<F^{-}<Al$
• B. $Na<Al<Mg<F$
• C. $Na<F^{-}<Al<Mg$
• D. $Na<F^{-}<Mg<Al$

Answer 1

The correct option is B

$Na<Al<Mg<F$

A positive ion is always smaller than a negative ion when they are isoelectronic species, so in this case ($N{a}^{+}$ is smaller than $F^{-}$ ).

Also, in a period the, size decreases from left to right and increases again at the end. So, Al would be smaller than Mg.